The physical and electromechanical properties of poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE))/poly(methylmethacrylate-b-dodecylmethacrylate-b-methylmethacrylate) (P(MMA-b-DDMA-b-MMA)) triblock copolymer blends were investigated. The P(VDF-TrFE)/P(MMA-b-DDMA-b-MMA) blend formed a well mixed and microphase-separated morphology in which the P(VDF-TrFE) was selectively miscible with the PMMA end blocks in the P(MMA-b-DDMA-b-MMA) triblock copolymer owing to the strong chemical affinity, not with the PDDMA middle block in the P(MMA-b-DDMA-b-MMA) block copolymer. The blends could manipulate the various nanostructures, such as hexagonal cylinder, lamellar, and micellar structures, according to the composition. The dielectric properties, tensile modulus, and electric actuation properties of the blends were easily tuned by simply changing the composition of the blend. It was found that the blend approach using a block copolymer serves as an easy and versatile way to fabricate the tunable polymer actuators.